Spider venoms are complex mixtures that contain hundreds of components, including neurotoxic peptides and proteins. The combination of the inherent complexity of spider venoms and the large number of spider species (~42,000 described) means that spider venoms contain a large array of toxin diversity that has only just begun to be explored. The aim of this research is to discover interesting peptides and proteins from the venom of the brown recluse spider and its relatives (the Sicariidae spiders), and then to characterize the structure and function of these peptides and proteins. We have previously explored the diversity of venom components from Sicariidae spiders by chromatographic separation of crude venom as well as by the analysis of cDNA libraries created from venom gland mRNA. These have helped us begin to understand the patterns of molecular evolution of these toxins and identify peptides for further study. In Specific Aim 1, interesting peptides will e expressed in bacteria using recombinant DNA techniques to generate samples for further structural and functional characterization. Structural characterization will be carried out using NMR (nuclear magnetic resonance) spectroscopy. In Specific Aim 2, the toxicity and method of action of these peptides will be characterized. The proposed research aims to characterize the structure and function of these venom components with the goals of discovery of novelty and analyses of structural evolution. Spider venom peptides and proteins are of interest for their potential use as therapeutic drugs and as tools for neurophysiology research, as many of them are believed to specifically inhibit or activate ion channels and receptors in nerve cells. In addition, some venom peptides are species-specific and therefore have the potential to be used as environmentally-friendly insecticidal toxins. PUBLIC HEALTH RELEVANCE: The proposed research aims to determine the structure and function of neurotoxic peptides and proteins identified from spider venoms. These components of spider venom are of interest for their potential use as therapeutic drugs and as tools for neurophysiology research, as many of them are believed to specifically inhibit or activate ion channels and receptors in nerve cells. In addition, some venom peptides are species-specific and therefore have the potential to be used as environmentally-friendly insecticidal toxins.